(solved)Arduino UNO problem with interrupts

Development Tools IDE 1.x
1

Hey guys!

I was using the Arduino UNO interrupts for the motor encoders when i started detecting an unexpected behaviour. Then i began searching for the problem and finally i ended up with just the Arduino UNO (no sensors, NOTHING connected). As explained in http://www.arduino.cc/en/Reference/AttachInterrupt the interrupts 0 and 1 correspond to ports 2 and 3 respectively. However this is not what i'm getting:

Pins 2, 3 and 4 respond to interrupt 0 (the one suposed to be attached to pin 0).

At the beginning i thought it could be due to some "internal short circuit / bad soldered pins" however after changing to another Arduino ONE board that I own i got the same result!!!

Is anybody getting this behavior as well?

Thanks,
Víctor.

2

Note that if you leave an input pin floating it will pick up random radio signals and capacitively couple to adjacent pins. This is also true of interrupt inputs. Add a pull-down or pull-up resistor and try your experiment again.

3

Thanks for your answer!! That was exactly the problem. Just for the report this simple code makes it clear:

int pin = 13;
volatile int state = LOW;

void setup()
{
  pinMode(pin, OUTPUT);
  pinMode(2, INPUT);
  digitalWrite(2, HIGH); // pull up resistor
  pinMode(3, INPUT);
  digitalWrite(3, HIGH); // pull up resistor
  
  attachInterrupt(0, blink1, RISING);
  attachInterrupt(1, blink2, RISING);
  
  Serial.begin(9600); // send and receive at 9600 baud
}

void loop()
{
  digitalWrite(pin, state);
}

void blink1()
{
  Serial.println("Called interrupt1");
  state = !state;
}

void blink2()
{
  Serial.println("Called interrupt2");
  state = !state;
}

Thanks again and best regards,

Víctor